1. Field of the Invention
The present invention concerns a card having electronic circuits that can exchange data and which are known in the industry as "smart cards."
The various new uses of the smart card show that this card is destined to fulfill increasingly complex functions, if its field of application is to be extended. This entails, then, the need to use increasingly bigger surface areas of chips to be integrated into these cards in order to fulfill these functions. This is the case, for example, with two known applications of chip cards, namely the telephone card and the bank card. The chip of the telephone card is a simple memory. It takes up a surface area of the order of one mm.sup.2. The chip of a bank card is a processor that integrates memory. It takes up a surface area of the order of 20 mm.sup.2.
It may briefly be recalled that a chip card is a relatively slim plastic card, wherein a semiconductor chip and a grid of conductors are inset in the thickness of the card. The chip is mounted on an upper surface of the grid, for example by bonding. Conductive wires are then soldered, firstly, to output terminals of the chip and, secondly, to metallizations of the grid. This is the chip card mounting technology known as the chip on board technology. A lower surface of the grid is flush with one of the two surfaces of the card, and forms the connector of the chip card. When this card is inserted into the reader, it is to this connector that the reader gets connected.
However, the standard support of the chip card is ill-suited to a chip with a large surface area. While the support is flexible, the chip for its part is very rigid. The bigger the chip, the more sensitive it is to strains and the greater are the chances of its being damaged. In practice, the effect of this is to reduce the reliability of the chip card, when it integrates a big chip. This restricts the possibility of extending the range of uses of the chip card, notably to novel applications.
2. Description of the Prior Art
Various known techniques have been used to resolve this problem. It has been attempted, notably, to reduce the extent of the strains on the chip and the wires that connect it to its grid of connectors. We might cite, for example, the known use of a slab of cobalt placed beneath the substrate of the chip to rigidify the chip. In another example, the method for making a cavity in the card is modified so that the chip can be received in order to rigidify the environment of the chip. However, in this chip card mounting technology, these approaches do not enable mounting on large surfaces, with areas of more than 20 mm.sup.2 for example. And, for surface areas such as this, numerous problems arise, notably the problem of the reliability of the chip thus mounted.
Besides, the plastic material that forms the card is not impervious to the various forms of ion and organic pollution to which the chips of the integrated circuit are very sensitive. The deterioration in reliability that is caused is all the more aggravated as the chip is big. This is a third technological limitation.
The mounting technology used is of the hybrid type. It is not optimized in terms of production. Indeed, semiconductor mounting technology uses a standard line for making a product in very large quantities. This product consists of one or more chips mounted in a standard package and called an electronic component. These chips may or may not be mutually interconnected. Beside these electronic components produced in large quantities, we therefore have a specific product, for example the chip card. Now this specific product is produced in far smaller quantities. And it too requires a specific production line. This considerably increases the production costs and depreciation costs of this line, as compared with those of production lines for standard products. Furthermore, the reject rate of this specific product is far higher than that of standard products because of the technology used. Indeed, the fixing of the wires is a delicate operation, the reliability of which directly affects the final product. These wires require specific protection to ensure that they do not deteriorate.
To circumvent these difficulties, it has also been attempted, in what is called "tape automatic bonding" technology, to connect metallization lead ends of the grid, particularly by hot transfer process, to the terminals of the chip. However, this technology also suffers from the degree of manufacturing precision that it requires. It too does not lead to sufficient reliability of mounting.
It is an object of the invention to overcome these drawbacks and enable the development of the chip card towards novel applications of greater complexity that are not hampered and restricted by the prior existence and use of magnetic cards, applications that might use, for example, an electronic key, in the sense of the electronic function and the shape of the object.
The invention uses conventional electronic packages provided with standard connection pins into which the function to be set up, comprising one or more chips conventional chips, is integrated. There is a known method of interconnecting several chips on a printed circuit and integrating the entire unit in a standard package. The reliability of the electronic component obtained is greater than that of the chips because the package mechanically shields the chip or chips of the electronic component from the various forms of ionic and organic pollution, and also because of the technology for mounting chips in a package, which is a standard technology that is well mastered. It is therefore possible to set up complex functions. However, a component such as this is not connectable as understood in the invention: for example, a component for surface mounting has pins that are too fine to provide for sure and reliable contact with the connector of a reader. A component mounted by insertion, for its part, may be inserted thousands of times in a connector: the pins will get bent or will even break and, in any case, the insertion operation is then a delicate one.